Patent GB-951089-A (GB)
Title: Improvements in or relating to the heat treatment carburizing or welding of metals
Inventor: TIMMINS JOHN
IPC: C21D1/70
Filed: 1960-07-06
Abstract: The formation of scale is reduced during the heat treatment of metals, such as ferrous metals, titanium or zirconium or alloys thereof, and nickel base alloys, by coating them with one or more layers of a sprayable mixture of an organophilic cation-modified clay and an organic solvent, such as toluene, xylene, naphtha, white or methylated spirit, benzene, aliphatic hydrocarbons, alcohols, esters or ketones, dipentene, turpentine or mineral oils, with or without a ceramic frit such as powdered glass or ceramics containing zircon or lead, a binder such as a polyester, polyamide, alkyd or silicone resin, dibutyl phthalate or shellac, and/or a filler such as china clay, water ground nepheline syenite or quartz, prior to heating in an atmosphere containing free oxygen at a temperature of at least 600 DEG C.  Also, for carburizing ferrous metals using a carburizing atmosphere, e.g. of isopropanol and methane, at a temperature of at least 600  DEG C., the metal surfaces to be protected are coated beforehand with one or more layers of the above mixture. Similarly, the above mixture may be used as a flux for arc-welding ferrous metals (see Division B3). Each layer may be applied by spraying, brushing or dipping, and then drying. The clay is modified by covering the surfaces of the particles with alkyl or aryl radicals coupled to the clay ionically by an onium base as described in Specifications 664,830 and 782,724 and U.S.A. Specification 2,531,440.  The bentonite group of clays are suitable for modifying. Examples of the modified clays are dimethyldioctadecyl ammonium montmorillonite or hectorite, and dodecylamine montmorillonite. The metal surfaces to be coated may first be degreased by washing with paraffin and treating with trichlorethylene vapour to remove organic material; paint may be removed with methylene chloride, and heavy scale by abrasive cleaning.  After heat treatment any scale may be removed by wet blasting with water or sand blasting followed by immersion in HCl for stainless steel, or by immersion in nitric acid and calcium fluoride bath for titanium and its alloys, e.g. 2% Cu, up to 0.1% C, up to 0.01% H, up to 0.2% Fe, balance Ti.  A zirconium alloy is disclosed of composition 1.5% Sn, 0.12% Fe, 0.05% Ni, 0.1% Cr. balance Zr.ALSO:The formation of scale is reduced during the heat treatment of metals, such as ferrous metals, titanium or zirconium or alloys thereof, and nickel base alloys, by coating them with one or more layers of a sprayable mixture of an organophilic cation-modified clay and an organic solvent, such as toluene, xylene, naphtha, white or methylated spirit, benzene, aliphatic hydrocarbons, alcohols, esters or ketones, dipentene, turpentine or mineral oils, with or without a ceramic frit such as powdered glass or ceramics containing zircon or lead, a binder such as a polyester, polyamide, alkyd or silicone resin, dibutyl phthalate or shellac, and/or a filler such as china clay, water ground nepheline syenite or quartz, prior to heating in an atmosphere containing free oxygen at a temperature of at least 600  DEG C.  Also, for carburizing ferrous metals using a carburizing atmosphere, e.g. of isopropanol and methane, at a temperature of at least 600  DEG C., the metal surfaces to be protected are coated beforehand with one or more layers of the above mixture.  Each layer may be applied by spraying, brushing or dipping, and then drying.  The clay is modified by covering the surfaces of the particles with alkyl or aryl radicals coupled to the clay ionically by an onium base as described in Specifications 664,830 and 782,724 and U.S.A. Specification 2,531,440.  The bentonite group of clays are suitable for modifying.  Examples of the modified clays are dimethyldioctadecyl ammonium montmorillonite or hectorite, and dodecylamine montmorillonite.  The metal surfaces to be coated may first be degreased by washing with paraffin and treating with trichlorethylene vapour to remove organic material; paint may be removed with methylene chloride, and heavy scale by abrasive cleaning.  After heat treatment any scale may be removed by wet blasting with water or sand blasting followed by immersion in HCl for stainless steel, or by immersion in nitric acid and calcium fluoride bath for titanium and its alloys.